Object graph editing context and methods of use

ABSTRACT

The present invention comprises a novel system for managing changes to a graph of data bearing objects In one embodiment, an object graph manager object referred to as an editing context is used to identify changes made to data bearing enterprise objects and to notify other interested objects when changes occur. As a result, data bearing objects need not themselves contain code necessary for monitoring changes. In another embodiment of the invention, the editing context is used to provide event-based &#34;undo&#34; capabilities. In another embodiment of the invention, each enterprise object has a primary key that is used to maintain the identification between an enterprise object instance and a corresponding database row. In another embodiment of the invention, multiple levels of editing contexts are used to provide multiple isolated object graphs, each of which allows independent manipulation of the underlying data bearing objects.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of object orientedapplication programming environments, particularly for applicationsaccessing databases.

2. Background Art

Object oriented programming languages are non-procedural programminglanguages in which program elements are viewed as objects that can passmessages to each other. An object includes its own data and programmingcode and is internally self-reliant. The programming code of an objectincludes procedures or methods. The methods of an object are invoked bymessages received from another object. Each object is an instance of anobject class. The properties of the objects in a class are defined by aclass definition. A class definition may utilize a hierarchical classstructure in which objects in the class inherit properties of a parentclass in addition to properties explicitly defined for the class. Thisinheritance property allows code for object classes to be customized forreuse in different applications, facilitating the sharing of programmingcode between different programs.

To write an application program in an object oriented programminglanguage, a programmer identifies the real-world objects of a problem,the data and processing requirements of those objects, and thecommunications needed between the objects, and encapsulates these inclass definitions. This process is simplified by taking advantage of theinheritance property of object classes by basing the class definitionsto the extent possible on preexisting object classes.

Objects are assembled in a modular fashion to create applications.Objects call on other objects to perform operations or procedures bysending appropriate messages. An appropriate message is a message towhich the receiving object can respond. The sending object musttherefore know the type of functions that a receiving object can performand be able to generate the corresponding message that will invoke thedesired operation. The sending object must also be prepared to acceptand process any resulting response.

Although objects are generally internally self-reliant, and cantherefore be viewed as modules that can be assembled with other objectsinto a variety of application programs, the simple assembling of objectsdoes not create a functional program. The objects must also be able toproperly interact and intercommunicate with each other. Although objectsrepresent reusable code, additional code must be written to provide forthe generation of appropriate outgoing messages and for processing andresponding to incoming messages.

One type of application program that is commonly used in business is adatabase application program. A database application program is aprogram that manipulates data stored in a database The database is oftenmanaged by a separate program, called a database management program,which has the ability to respond to requests to store, retrieve, searchfor, extract and update data in the database. In order to access data inthe database, the database application program must generate appropriatedatabase requests to the database management program.

There are many types of database structures and many kinds of databasemanagement programs. In order to be able to access a particulardatabase, a database application program must know the structure of thedatabase and the syntax used by the database management program. Asthese can vary from one database to another, a single databaseapplication program cannot generally be used with different databases.Instead, separate versions of a database application program are neededto deal with different databases and different database managementprograms.

Two types of database structures are flat file databases and relationaldatabases.

A flat file database can be viewed as a single large table having anumber of rows and a number of columns. Each row ("record") correspondsto a particular entity, and each column of that row ("field")corresponds to a particular attribute of that entity. For example, anemployee database may contain information about employees, includingname, address, social security number, salary, department, etc. Each rowwould correspond to a particular employee. Separate columns wouldcorrespond to name, address, social security number, salary, department,etc., respectively. One of the columns contains an entry that uniquelyidentifies each row. This entry is often called the "primary key". Forthe employee database example, the primary key might be the employee'sname, the social security number, or an index number generated by thedatabase management program. To find the salary for Jane Doe in theemployee database, for example, one would look in the row correspondingto Jane Doe, and read off the salary in the salary column. In a flatfile, the only data available about an entity is the informationcontained in the row corresponding to the entity, that is, only theinformation for which there is a column, or "field", in the table.

In a relational database, information in one table may be related toinformation in other tables. For example, a company database may includean employee name and address table that contains a row for eachemployee, with fields for the name and address of each employee in eachrow. The database may also contain a departmental table that contains arow for each department, with each row containing a department ID fieldas well as fields for the names of all employees in the department. Thedepartmental table may be linked to the employee name and address tableby including a field for the department ID in the employee name andaddress table. This department ID, called a "foreign key", may be viewedas a pointer from the employee name and address table to thedepartmental table, indicating where additional related data may befound.

An example of a database application program that might use therelational database described in the preceding paragraph is anapplication that compiles the names and addresses of all employees of aparticular department This application might operate as follows. First,the application program requests the database management program toextract the names of all employees in the department in question fromthe departmental table. To do so, the application program needs to knowthe structure of the departmental table, and needs to formulate therequest in the specific syntax of the database management program. Then,for each employee name obtained, the application program requests thecorresponding address from the employee name and address table. Again,the application program must know the structure of the name and addresstable and needs to formulate the request, or in this case the series ofrequests, one for each employee name, in the correct syntax. Theapplication program then needs to assemble the received data into acoherent form and display it to a user. The application program for eventhis simple function is complicated: the program must know about thestructure of the tables in the database, must be able to generate avariety of database requests in the particular syntax of the databasemanagement program, must be able to process the data received, and mustbe able to assemble the data and display it on a user interface.

Database application program writing may be simplified by using objectoriented programming techniques. Objects can be constructed that performinput and output functions such as requesting data from a databasemanager program or displaying data on a user interface. An applicationprogram therefore need not be provided with code for handling theselower level functions. The application program can let appropriateobjects take care of these and other requirements. Writing theapplication program is simplified.

Object oriented programming environments provide tools to programmerssuch as predefined object classes that can simplify the building ofapplications.

One prior art set of tools and resources for an object orientedprogramming environment that can be used to build database applicationsis Enterprise Objects Framework 1x (TM), a set of tools and resourcesfor the NEXTSTEP (TM) object oriented programming environment from NeXTComputer, Inc.

The architecture and data flow of an Enterprise Objects Framework 1xapplication is shown in FIG. 1. In the application shown in FIG. 1, dataflows from a relational database 100 to a user interface 160, and viceversa, via a number of intervening modules and levels. Each of theblocks shown in FIG. 1 constitutes a portion of the overall applicationprogram and may be made up of one or more objects.

The flow of data from the relational database 100 to user interface 160proceeds as follows. Data in the form of rows of data from relationaldatabase 100 are retrieved from relational database 100 to an adaptorlevel 110, using well-known relational database access techniques. Atadaptor level 110, the raw data received from relational database 100 ispackaged into "dictionary objects." Dictionary objects contain key-valuepairs: each key typically represents the name of a database column, andthe key's value corresponds to the data for the column of the particularrow that was read from relational database 300. As shown in FIG. 1, datain the form of these dictionary objects is passed from adaptor level 110to database level 120.

Database level 120 creates "enterprise objects" from the dictionaryobjects. Enterprise objects are like other objects used in objectoriented programming languages in that they couple data with methods foroperating on that data. However, under Enterprise Objects Framework 1x,an enterprise object has certain characteristics that distinguish itfrom other object classes. An enterprise object has properties that mapto stored data, and an instance of an enterprise object typicallycorresponds to a single row or record in a database. Further, anenterprise object knows how to interact with other parts of theEnterprise Object Framework to give and receive values for itsproperties The ingredients that make up an enterprise object are itsclass definition and the data values for the row or record to which itcorresponds. The enterprise object also contains pointers to otherenterprise objects created from rows of related database tables. Theseother enterprise objects typically contain yet other pointers to otherrelated objects. The entire set of enterprise objects used by anapplication program thus forms an interconnected graph of data bearingenterprise objects. This graph constitutes a particular view of theunderlying database.

The enterprise objects created at database level 120 are passed fromdatabase level 120 to data source 130. Data source 130 is an object thathas the ability to fetch, insert, update and delete enterprise objects.As such it is both a source and a sink for enterprise objects. Changesmade by data source 130 to an enterprise object are passed down viadatabase level 120 and adaptor level 110 to relational database 100 sothat a corresponding change is made to the database for a change made toan enterprise object. The data source 130 does not know the structure ofthe underlying database. Those details are taken care of by adaptorlevel 110. Accordingly, as long as the appropriate adaptor 110 is used,the same data source 130 can be used for a variety of differentdatabases.

Data source 130 supplies enterprise objects created at database level120 to controller 140. As shown in FIG. 1, controller 140 transportsdata in the form of values from the enterprise objects to user interface160 via association objects 150. Controller 140 coordinates the valuesdisplayed in the user interface with the corresponding enterprise objectvalues. When enterprise objects are modified in the user interface,controller 140 tells data source 130, which is responsible forpropagating changes to relational database 100.

In Enterprise Objects Framework 1x, changes to enterprise objects mustbe made by editing values in the user interface or by using thecontroller method "setValues:for Object:." Because enterprise objectstypically include the business logic needed for the application, itwould be useful if enterprise objects could be worked on by anapplication program in the same way most objects are worked on: i.e. bysending an enterprise object an appropriate message. However, becausethe integrity of the underlying database must be maintained, certainprocedures performed on enterprise objects, such as procedures that makechanges to the data in an enterprise object, must be specially handled.For example, changes made directly by sending a message to an enterpriseobject in Enterprise Objects Framework 1x bypass controller 140.Accordingly, as controller 140 controls messages to the user interface160 and the database level 120, these changes are not updated in theuser interface and are not saved in the database. In order for thesechanges to propagate to the user interface and the database, theenterprise object itself must keep track of changes and must explicitlynotify controller 140 when changes occur. This requirement requiresadditional code in each enterprise object, making the building ofenterprise objects, and applications using enterprise objects, morecomplicated and time consuming than other kinds of object orientedprogramming.

Another limitation of Enterprise Objects Framework 1x is that becausecontroller 140 is tightly coupled to user interface 160, controller 140is not usable for database server and other non-user interfaceapplications. Accordingly, buffering and undo functions that areimplemented in controller 140 in Enterprise Objects Framework 1x are notavailable for applications written for server platforms.

SUMMARY OF THE INVENTION

The present invention comprises a novel system for managing changes to agraph of data bearing objects. In one embodiment, an object graphmanager object referred to as an editing context is used to identifychanges made to data bearing enterprise objects and to notify otherinterested objects when changes occur. As a result, data bearing objectsneed not themselves contain code necessary for monitoring changes. Inthis embodiment, a data bearing object broadcasts a "willChange" messageto a list of observer objects, one of which is the editing context,prior to undergoing any changes. Upon receiving the "willChange"message, the editing context takes a "snapshot" of the object prior tothe change. After the change is made, and the change is to be committedto the database, the editing context takes a second snapshot of theobject. The editing context uses snapshot differencing to identify thechange that occurred, and then records the change in the database. Theediting context also registers other objects, for example user interfaceobjects, that need to be notified if the object has changed, andnotifies these registered objects when a change occurs.

In another embodiment of the invention, the snapshots recorded by theediting context are used to provide event-based "undo" capabilities. Inthis embodiment, a change event begins, and a data bearing object aboutto be changed broadcasts a "willChange" message. The editing contextreceives the "will Change" message and takes a snapshot The editingcontext ignores succeeding "willChange" messages from the object untilthe change event is completed. At that point, the editing contextrecords the snapshot on an undo stack. This way, undo's are bracketed bya "willChange" message and the end of a change event. Intermediatechanges are not recorded.

In another embodiment of the invention, each enterprise object has aprimary key that is used to maintain the identification between anenterprise object instance and a corresponding database row. In thisembodiment, the editing context monitors the creating of new enterpriseobjects to insure that another instance of an enterprise object is notcreated when a row with the same primary key is fetched from thedatabase.

In another embodiment of the invention, multiple levels of editingcontexts are used to provide multiple isolated object graphs, each ofwhich allows independent manipulation of the underlying data bearingobjects. In this embodiment, an underlying editing context providesobjects from its object store to one or more overlying editing contexts.Each of the overlying editing contexts creates and manages its ownobject store containing copies of the objects in the underlying editingcontext. Changes can be made to objects in an overlying object graphwithout effecting the state of the same objects in the underlying objectgraph or in the other object graphs. When a change is final, the changecan be passed down to the underlying editing context, and passed up tothe other overlying object graphs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block level diagram illustrating a database application ofthe prior art.

FIG. 2 is a block level diagram illustrating one embodiment of adatabase application of the present invention.

FIG. 3 is a block diagram showing how the editing context of oneembodiment of the present invention performs the functions of changetracking and notification.

FIG. 4 is a block diagram showing how the user interface is updated inresponse to an update message from the editing context in one embodimentof the present invention.

FIG. 5 is a block diagram showing how one embodiment of the editingcontext of the present invention performs the function of objectuniquing.

FIG. 6 is a block diagram showing how one embodiment of the editingcontext of the present invention performs the function of saving changesto enterprise objects.

FIG. 7 is a block diagram showing how one embodiment of the editingcontext of the present invention provides undo functionality.

FIG. 8 is a schematic diagram showing the structure of one embodiment ofthe present invention.

FIG. 9 is a schematic diagram showing the structure of one embodiment ofthe object store of the present invention including multiple adaptorlevels and multiple databases.

FIG. 10 is a schematic diagram showing the structure of one embodimentof the object store of the present invention including multiple networklinked databases.

FIG. 11 is a schematic diagram showing the structure of one embodimentof the present invention including multiple nested editing contexts.

FIG. 12 is a schematic diagram of one embodiment of a computer system onwhich the present invention may be implemented.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent to one skilled in the art, however, that the presentinvention may be practiced without these specific details. In otherinstances, well-known features have not been described in detail inorder not to unnecessarily obscure the present invention.

The general structure of one embodiment of a database applicationprogram utilizing the present invention is shown in FIG. 2. Thisembodiment is used in the Enterprise Objects Framework 2.0 databaseapplication programming package from NeXT Software, Inc., assignee ofthe present invention. Enterprise Objects Framework 2.0 is described inthe Enterprise Objects Framework Developer Guide, preliminary release,attached hereto as Appendix A.

In the application shown in FIG. 2, like in the prior art applicationshown in FIG. 1, data flows from a relational database 200 to a userinterface 260, and vice versa, via a number of intervening modules andlevels. Each of the blocks shown in FIG. 2 constitutes a portion of theoverall application program and may be made up of one or more objects.Although certain of the modules shown in FIG. 2 are similar to thoseshown in FIG. 1, there are certain significant differences, as outlinedbelow.

The modules shown in FIG. 2 are a database 200, and adaptor level 210, adatabase level 220, an editing context 225, a data source 230, a displaygroup 240, associations 250, and user interface 260. As shown in FIG. 2,these modules are divided into three layers. Database 200, adaptor level210, and database level 220 constitute access layer 270. Editing context225, data source 230, and display group 240 constitute control layer280. Associations 250 and user interface 260 constitute interface layer290.

The flow of data from the relational database 200 to user interface 260proceeds as follows. Data in the form of rows of data from relationaldatabase 200 are retrieved from relational database 200 to an adaptorlevel 210, using well-known relational database access techniques.Adaptor level 210 consists of an adaptor that translates databaserequests received from database level 220 to the correct syntax andformat for the particular database 200 being accessed. For example, ifdatabase 200 is an Oracle database, an Oracle adaptor level 210 is used.If data base 200 is a Sybase database, a Sybase adaptor level 210 isused. In this way, every module above adaptor level 210 is databaseindependent.

At adaptor level 210, the raw data received from relational database 200is packaged into "dictionary objects." Dictionary objects containkey-value pairs: each key typically represents the name of a databasecolumn, and the key's value corresponds to the data for the column ofthe particular row that was read from relational database 200. As shownin FIG. 2, data in the form of these dictionary objects is passed fromadaptor level 210 to database level 220.

Database level 220 creates "enterprise objects" from the dictionaryobjects. Unlike the embodiment of FIG. 1, the enterprise objects of thepresent invention need not have any special knowledge about theunderlying database or need to include methods for monitoring changes,other than being able to send "willChange" messages, as described below.In addition, unlike the embodiment of FIG. 1, in which the enterpriseobjects created at database level 120 were passed directly to datasource 130, in the embodiment of FIG. 2, there is an additional module,editing context 225, between database level 220 and data source 230. Aswill be discussed in detail below, editing context 225 provides many ofthe inventive features of the present invention. Enterprise objectscreated at database level 220 are passed from database level 220 toediting context 225.

Editing context 225 functions as the manager of the object graph createdby the application of FIG. 2 from database 200. Important functionsperformed by editing context 225 include object uniquing, user interfacenotification, change notification, change tracking, save notification,and providing undo capabilities.

Upon receiving an enterprise object from database level 220, editingcontext 225 registers each enterprise object in a lookup table, usingits primary key or other unique identifier to uniquely identify theobject to the external database 200, as part of its uniquing function toensure that only one enterprise object is created in the object graphmanaged by editing context 225 for each database row.

Enterprise objects in Enterprise Object Frameworks 2.0 have the abilityto register any other object as an observer. An observer is an objectthat is interested in any changes made to the objects with which it isregistered as an observer. Editing context 225 registers itself as anobserver of each enterprise object that is part of its object graph.

Data source 230 is an object that acts as an interface between displaygroup 240 and editing context 225. It forwards requests for insertionand deletion of objects from display group 240 to editing context 225.Changes made by editing context 225 to an enterprise object are passeddown via database level 220 and adaptor level 210 to relational database200.

Display group 240 acts as the interface between interface layer 290 andcontrol layer 280. It is the mechanism by which interface layer 290accesses stored data. Editing context 225 supplies enterprise objectscreated at database level 220 via data source 230 to display group 240.As shown in FIG. 2, display group 240 transports data in the form ofvalues from the enterprise objects to user interface 260 via associationobjects 250. Display group 240 coordinates the values displayed in theuser interface with the corresponding enterprise object values. Whenenterprise objects are modified in the user interface, editing context225 tracks the changes, and propagates changes, as appropriate, torelational database 200.

FIG. 3 is a block diagram showing how the editing context of oneembodiment of the present invention performs the functions of changetracking and notification. As shown in FIG. 3, at block 320, the editingcontext registers itself as an observer of all enterprise objects in itsobject graph. This ensures that any enterprise object that is about toundergo a change will first send a "willChange" message to the editingcontext. In the embodiment shown in FIG. 3, the editing context receivessuch a "willChange" message from an enterprise object about to undergo achange event at block 330

After receiving a "willChange" message, the editing context records asnapshot of the object that sent the message at block 340. At block 350,the editing context awaits the receipt of an end of event messageindicating the end of the event that caused the issuance of the"willChange" message.

The generating of "willChange" and end of event messages may for exampleproceed as follows. The operating system of the computer system usingthe embodiment of FIG. 3 receives notification of an event. Events mayhave a variety of forms, depending on the operating system. Examples ofevents are user events such as moving a mouse, clicking a mouse button,or pressing a key, as well as network events such as remote procedurecalls or other network messages.

After receiving notification of an event, the event manager of theoperating system in turn sends notification of the event to theapplication code. The application code then executes as appropriate inresponse to the event. If, as part of the execution of the applicationcode, a change is made to an enterprise object, the enterprise objectbroadcasts a "willChange" message to its observer objects, including theediting context. Upon receiving the "willChange" message, the editingcontext sends the event manager of the operating system a messagerequesting that the editing context be called back by the operatingsystem after the execution of the application code triggered by theevent has been completed. The application code executes to completion,and the operating system sends the editing context a message indicatingthe end of the event.

Once the editing context receives an end of event message at block 360,the editing context broadcasts a change message at block 370 to thoseother objects that have registered themselves with the editing contextas observers of the changed object. In certain situations, for examplewhen it is desired to preserve referential integrity, such as bypropagating deletes, the editing context may at this point also take asecond, post change snapshot of the object.

In order to ensure that the user interface is updated properly inresponse to changes made to an enterprise object, display group 240 mayregister itself as an observer with the editing context. Display group240 is therefore notified when any enterprise objects whose values aredisplayed on the user interface are changed Display group 240 can thenupdate all of the values in the display. The purpose updating all thedisplayed values is to ensure that all values displayed in the userinterface reflect the change made to the enterprise object. Some of thevalues displayed in the interface may be derived values calculated fromthe changed data. If only the changed data is updated in response to thechanged data message sent by the editing context at block 370, but notany displayed data derived from the changed data, then the datadisplayed in the user interface would be inconsistent. By updating allthe data displayed in the user interface, the display group assures thatthe user interface is consistent FIG. 4 is a block diagram showing howthe user interface is updated by the display group in response to anchanged object message from the editing context in one embodiment of thepresent invention. As shown in FIG. 4, display group receives a messageindicating changes made to an enterprise object, corresponding to themessage sent by the editing context at block 370 of FIG. 3, at block410. The user interface then obtains the new values for the changedenterprise object at block 430. In one embodiment, the changed valuesare contained in the message received from the editing context at block410. In another embodiment, the message received from the editingcontext at block 410 contains the identity of the changed object but notthe changes themselves. In this embodiment, the user interface obtainsthe changed values by querying the changed enterprise object directly.

After obtaining the changed values, the user interface calculates anyderived values at block 440. Finally, all values displayed by the userinterface are updated with at block 450.

FIG. 5 is a block diagram showing how one embodiment of the editingcontext of the present invention performs the function of objectuniquing. As shown in FIG. 5, the editing context receives the requestfor a new enterprise object at block 510. This request may come, forexample, from data source 230 of FIG. 2. After receiving the request,the editing context checks to see whether an instance of the requestedobject already exists at decision block 520. If an instance of theobject already exists, the editing context transmits the existing objectto the requester at block 570. If no instance of the object exists, theediting context passes a request for the object from its underlyingobject store, which may consist, for example, of database level 220,adaptor level 210, and database 200 of FIG. 2. After receiving therequested object from the object store at block 540, the editing contextregisters a unique identifier of the object at block 550 and transmitsthe new object to the requester at block 560.

FIG. 6 is a block diagram showing how one embodiment of the presentinvention performs the function of detecting and saving changes toenterprise objects in the underlying database or other object store. Asshown in FIG. 6, after the editing context receives a "willChange"message from an enterprise object at block 610, the editing contexttakes a snapshot of the object in its unchanged state at block 620. Theediting context then awaits a commit message indicating that a changehas been completed and that the changed data is to be committed to thedatabase at block 630. The editing context may receive additional"willChange" messages from the enterprise object between the time itreceives the initial "willChange" message and the commit message, butthese additional "willChange" messages are ignored. After the editingcontext receives a commit message at block 640, the editing contexttakes a second snapshot of the enterprise object at block 650. At block660, the editing context sends a change request to the object store tosave the change made to the enterprise object. The object store detectsthe change by comparing the first and second snapshots and stores thechange at block 670.

In the embodiment of FIG. 2, the object store comprises the access layer290 and database 200. The object store may also be any other entity ormechanism that appears to the editing context to function in a databaselevel like manner: that is, it stores and retrieves enterprise objectdata in response to data base requests from the editing context.

FIG. 7 is a block diagram showing how one embodiment of the editingcontext of the present invention provides undo functionality. At block710, the editing context receives a "willChange" message from anenterprise object, indicating that the enterprise object anticipatesundergoing a change. At block 715, the editing context checks to seewhether a snapshot for the current change event has already been taken.A change event is a set of one or more successive changes made to anenterprise object within the pre-defined limits of the change event. Forexample, a change event may occur when a user makes several successivechanges in a user interface to observe the results. In this case, thechange event would commence when the first change is entered and theenterprise object sends out an initial "willChange" message. The changeevent may be deemed to continue until the user activates a save commandor moves a mouse pointer to another data field.

If a snapshot has already been taken during the current change event,the current "willChange" message is ignored. If no snapshot has beentaken, the editing context takes a snapshot at block 720. At block 730,the editing context places the snapshot into a "recent snapshot table".The recent snapshot table acts as a holding place for the snapshot untilit is placed on the undo stack, as described below.

After placing the snapshot in the recent snapshots table, the editingcontext awaits a end of event message, indicating that the currentchange event has ended, at block 740. Upon receiving the end of eventmessage at block 750, the editing context, at block 760, records thesnapshot stored in the recent snapshot table at block 730 on the undostack. Finally, the editing context clears the recent snapshot table atblock 770. The result is that the top level of the undo stack nowcontains a snapshot of the object prior to the changes made during thechange event. The changes made can therefore be undone by changing theenterprise object back to the state reflected in the topmost snapshot inthe undo stack.

The snapshots on the undo stack allow successive reversion of the stateof the enterprise object to the states captured in each snapshot of thestack. By bracketing the snapshots, and therefore the captured states ofthe object, between the initial "willChange" message and a correspondingend of a change event, short-term, intermediate changes in theenterprise object are ignored. Instead of inefficiently filling the undostack with every little incremental change in the state of theenterprise object, only significant changes are recorded, resulting inan efficient and fast undo facility.

In the prior art, in order to provide an undo capability, undo code hadto be written into the application program, resulting in the investmentof substantial coding time and effort, and creating the opportunity fora variety of errors. By using the undo facilities of the presentinvention described above, however, an application program automaticallyobtains undo capabilities without the need of complex coding and withlittle risk of error.

Although the user interface update, object uniquing, data saving, andundo capabilities of the editing context of the present invention havebeen described with respect to the separate embodiments of FIGS. 3, 5,6, and 7, respectively, a single editing context of the presentinvention may provide some or all of these capabilities concurrently.

In each of the embodiments of the present invention described above withrespect to FIGS. 2-7, the editing context functions on behalf of one ormore application programs as the manager of an object graph obtainedfrom an underlying data storage entity referred to by the generic name"object store". This basic structure is shown in FIG. 8, which showsediting context 820 managing object graph 825 on behalf of applications805, 810 and 815.

Object graph 825 represents a particular view of the database structureunderlying object store 830. From the point of view of editing context820, object store 830 represents a source of new objects and a sink forchanged objects. As described above, object store 830 may consist of theaccess layer 290 and database 200 of FIG. 2. However, object store 830may consist of other entities and/or systems that can respond torequests from editing context 820 to perform database functions relatedto object graph 825 managed by editing context 820.

FIGS. 9-10 illustrate example embodiments of structures that can be usedas object store 830. From the point of view of the editing context, eachof these embodiments looks the same.

FIG. 9 is a schematic diagram showing the structure of one embodiment ofthe object store of the present invention including multiple adaptorlevels and multiple databases. In this embodiment, the object storeconsists of an object store coordinator 905, three different databases940, 945, and 950, respectively, three corresponding adaptor levels 925,930, and 935, respectively, and three corresponding database levels 910,915, and 920, respectively. The three databases may be managed bydifferent database management systems. For example, database 940 may bean Oracle database, database 945 may be a Sybase database, and database950 may be another database. Object store coordinator 905 coordinatesdatabase requests received from editing context 900, decides whichdatabase corresponds to each request received, and sends the appropriatemessage to the appropriate database level, which, via the correspondingadaptor level, performs the database function requested. If the requestfrom editing context 900 involves updating data contained in anenterprise object, object store coordinator 905 identifies the databasecorresponding to the changed data and sends an appropriate message tothe corresponding database level. If the request from editing context900 involves the creation of a new enterprise object, object storecoordinator 905 performs the required object to database mapping andextracts the appropriate data from one or more of the databases.

In the embodiment of FIG. 9, the multiple databases are all part of asingle computer system. However, the databases may be spread overdifferent machines in a computer network, as shown in FIG. 10.

The embodiment of FIG. 10, like the embodiment of FIG. 9, includes anediting context 1000, an object store coordinator 1005, three databaselevels 1010, 1015, and 1020, and three corresponding adaptor levels1025, 1030, and 1035. The embodiment of FIG. 10 also include threedifferent databases 1060, 1065, and 1070. However, instead of beingdirectly connected to their corresponding adaptor levels, databases1060, 1065, and 1070 are distributed over a network, and managed byseparate database servers 1045, 1050, and 1055, respectively.Accordingly, instead of directly accessing a connected database as inFIG. 9, in the embodiment of FIG. 10, an adaptor level contacts itscorresponding database by sending a network message to the appropriatedatabase server. In this embodiment, object store coordinator 1005coordinates database requests received from editing context 1000,decides which database corresponds to each request received, and sendsan appropriate message to the applicable database level. The databaselevel transmits a corresponding message to its adaptor level, whichformulates the appropriate network message to the appropriate databaseserver to perform the database function requested. If the request fromediting context 1000 involves updating data contained in an enterpriseobject, object store coordinator 1005 identifies the databasecorresponding to the changed data and sends an appropriate message tothe corresponding database level. The database level sends acorresponding message to its adaptor level, which transmits anappropriate network message to the applicable database server. If therequest from editing context 1000 involves the creation of a newenterprise object, object store coordinator 1005 performs the requiredobject to database mapping and extracts the appropriate data from one ormore of the databases, again via the applicable database level, adaptorlevel, network, and database server. Again, the complexities underlyingediting context 1000 are hidden. Editing context 1000 interacts withobject store coordinator 1005 in the same manner as with database level220 in the simple structure of FIG. 2.

FIG. 11 is a schematic diagram showing the structure of one embodimentof the present invention including multiple nested editing contexts.This embodiment is similar to the embodiment of FIG. 8. However, insteadof having an editing context 820 managing an object graph 825 formultiple applications 805, 810 and 815, as in FIG. 8, in the embodimentof FIG. 11, editing context 1145 manages object graph 1150 on behalf ofthree other editing contexts 1115, 1120 and 1125, respectively. Each ofthese other editing contexts manages its own object graph on behalf ofits own application, which may be a separate application program, butmore typically is a separate task being performed by a singleapplication program. For example, each application may consist of aseparate window looking at different or the same views of the underlyingdata. As such, editing context 1115 manages object graph 1130 on behalfof application 1100, editing context 1120 manages object graph 1135 onbehalf of application 1105, and editing context 1125 manages objectgraph 1140 on behalf of application 1110. To each of editing contexts1115, 1120, and 1125, editing context 1145 looks like an object store830 of FIG. 8. Conversely, each of editing contexts 1115, 1120 and 1125looks to editing context 1145 of FIG. 11 like an application program805, 810, or 815 of FIG. 8. Each of editing contexts 1115, 1120 and 1125manages a separate object graph 1130, 1135, and 1140, respectively.Object graphs 1130, 1135, and 1140 constitute independent views of thedata provided by editing context 1145. As each object graph is createdindependently, there may be multiple instances of enterprise objectsspread across object graphs 1130, 1135 and 1140, respectively. Each ofapplications 1100, 1105 and 1110 can therefore independently work andmake changes to separate instances of the same enterprise objects. Whenan application program 1100, 1105 or 1110 wishes to commit a change tothe database, a commit change to database message is sent to editingcontext 1145. Editing context 1145 then updates the appropriateenterprise objects in its object graph 1150, and also broadcasts achange message to editing contexts 1115, 1120 and 1125, respectively.Editing contexts 1115, 1120 and 1125 may or may not pass these changeson to their respective applications 1100, 1105 and 1110, depending onthe particular configuration and purpose of the application programs.Editing context 1145 does not commit the changes to underlying objectstore 1155 unless it receives an explicit message to do so. Each of theediting contexts 1115, 1120, 1125 and 1145 may in general perform any ofthe functions for an editing context described with respect to FIGS.2-7.

The nested editing context structure of FIG. 11 provides a simplifiedmeans for creating-a database application program utilizing "drill downuser interfaces." Drill down user interfaces consist, for example, of aseries of pop-up windows that can be used to make changes to datadisplayed in a window. For example, a window may display the employeesof a department, their salaries, and department budget data. Adepartment manager may wish to be able to investigate various "what if"scenarios without actually changing the underlying database. Anapplication program may be designed to allow the manager to pop up asecond window in which the manager can make various changes in thedisplayed data to see what the resultant effects are. When the manageris satisfied with the changes, a command button might be provided tocommit the changes to the database.

In the prior art, designing such an application was complex. To createthe pop-up window, the application had to copy values from theunderlying database objects to local variable, which would be displayedin the pop up window. The application would also have to recreate thevalidation methods of the underlying objects and take into account anyderived values. Once changes to the local variables were to becommitted, the application would have to manually harvest the changedvalues and transmit them to the underlying objects.

The present invention provides a much less complex way to design drilldown interfaces. By using nested editing contexts and thereby creatingindependent copies of the underlying enterprise objects, instead ofhaving to create and deal with local variables, the enterprise objectsthemselves can be manipulated in a pop-up window. Accordingly, the samecode can be used to manipulate data in the pop up window as is used inthe main window Because the user operates on copies of the objects,instead of on derived local variables, all methods of the object arepreserved. The present invention thus provides a simpler and less errorprone way to create application programs using drill down interfaces.

The present invention can be implemented by means of softwareprogramming on any of a variety of one or more computer systems as arewell known in the art, including, without limitation, computer systemssuch as that shown in FIG. 12. The computer system shown in FIG. 12includes a CPU unit 1200 that includes a central processor, main memory,peripheral interfaces, input-output devices, power supply, andassociated circuitry and devices; a display device 1210 which may be acathode ray tube display, LCD display, gas-plasma display, or any othercomputer display; an input device 1230, which may include a keyboard,mouse, digitizer, or other input device. The computer system may or maynot include non-volatile storage 1220, which may include magnetic,optical, or other mass storage devices. The computer system may alsoinclude a network interface 1240 allowing the computer system tocommunicate with other systems over a communications network. Any of avariety of other configurations of computer systems may also be used.

Thus a novel method and apparatus for managing an object graph of databearing objects was presented. Although the present invention has beendescribed with respect to certain example embodiments, it will beapparent to those skilled in the art that the present invention is notlimited to these specific embodiments.

We claim:
 1. In a computer system, a method for monitoring changes madeto an object graph comprising a plurality of data bearing objectscontaining data from a database comprising the steps of:prior to makingany change to a first data bearing object in said object graph inresponse to an event that initiates execution of application code,transmitting a message indicating that said first data bearing objectexpects to undergo a change from said first data bearing object to anobject graph manager; taking a snapshot of said first data bearingobject upon said object graph manager receiving said message indicatingsaid expected change; making one or more changes to said first databearing object during said execution of application code in response tosaid event; transmitting a message indicating an end of said executionof application code in response to said event to said object graphmanager.
 2. The method of claim 1 further comprising the stepsof:transmitting a message indicating that said first data bearing objecthas undergone a change from said object graph manager to an interestedobject.
 3. The method of claim 2 wherein said interested object is anobject registered with said object graph manager as an object to beinformed of any changes to said first data bearing object.
 4. The methodof claim 1 wherein said step of transmitting a message indicating thatsaid first data bearing object expects to undergo a change comprises thesteps of:registering said object graph manager as an observer with saidfirst data bearing object; broadcasting said message indicating thatsaid first data bearing object expects to undergo a change from saidfirst data bearing object to registered observers of said data bearingobject.
 5. The method of claim 2 wherein said interested objectcomprises a user interface manager object managing values displayed in auser interface, and further comprising the steps of:after said userinterface manager object has received said message indicating that saidfirst data bearing object has undergone a change, transmitting a messagefrom said user interface manager object to said first data bearingobject requesting values for data of said first data bearing object;transmitting said values for said data of said first data bearing objectfrom said first data bearing object to said user interface managerobject, updating said values displayed in said user interfacecorresponding to said values for said data of said first data bearingobject.
 6. In a computer system, a method for modifying a database inaccordance with changes made to an object graph comprising a pluralityof data bearing objects containing data from said database comprisingthe steps of:prior to making any change to a first data bearing objectin said object graph, transmitting a message indicating an expectedchange to said first data bearing object to an object graph manager;taking a snapshot of said first data bearing object upon said objectgraph manager receiving said message indicating said expected change;making one or more changes to said first data bearing object;transmitting a commit message to said object graph manager requestingthat changes made to said first data bearing object be committed to saiddatabase; taking a second snapshot of said first data bearing objectupon said object graph manager receiving said commit message; detectingsaid one or more changes to said first data bearing object by comparingsaid second snapshot to said first snapshot; storing data correspondingto said detected one or more changes in said database.
 7. The method ofclaim 6 wherein said step of storing data corresponding to said detectedone or more changes in said database comprises the step of sending achange request from said object graph manager to an object store.
 8. Themethod of claim 7 wherein said object store comprises an object storecoordinator that interfaces between said object graph manager and aplurality of databases.
 9. The method of claim 8 wherein said pluralityof databases comprise databases distributed over a computer network. 10.In a computer system, a method for undoing changes made to an objectgraph comprising a plurality of data bearing objects containing datafrom a database comprising the steps of:prior to making any change to afirst data bearing object in said object graph in response to an eventthat initiates execution of application code, transmitting a messageindicating that said first data bearing object expects to undergo achange from said first data bearing object to an object graph manager;taking a snapshot of said first data bearing object upon said objectgraph manager receiving said message indicating said expected change;making one or more changes to said first data bearing object during saidexecution of application code in response to said event; transmitting amessage indicating an end of said execution of application code inresponse to said event to said object graph manager; recording saidsnapshot on an undo stack.
 11. The method of claim 10 further comprisingthe step of determining whether a previous snapshot of said data bearingobject has already been taken during said execution of application codein response to said event prior to taking said snapshot of said databearing, and taking said snapshot only if no such previous snapshot hasbeen taken.
 12. The method of claim 10 further comprising the stepsof:recording said snapshot in a recent snapshot table after taking saidsnapshot; clearing said recent snapshot table after recording saidsnapshot on said undo stack.
 13. A program storage device readable by amachine, tangibly embodying a program of instructions executable by themachine to perform method steps for monitoring changes made to an objectgraph comprising a plurality of data bearing objects containing datafrom a database, said method steps comprising the steps of:prior tomaking any change to a first data bearing object in said object graph inresponse to an event that initiates execution of application code,transmitting a message indicating that said first data bearing objectexpects to undergo a change from said first data bearing object to anobject graph manager; taking a snapshot of said first data bearingobject upon said object graph manager receiving said message indicatingsaid expected change; making one or more changes to said first databearing object during said execution of application code in response tosaid event; transmitting a message indicating an end of said executionof application code in response to said event to said object graphmanager.
 14. The program storage device of claim 13 in which said methodsteps further comprise the steps of:transmitting a message indicatingthat said first data bearing object has undergone a change from saidobject graph manager to an interested object.
 15. The program storagedevice of claim 14 wherein said interested object is an objectregistered with said object graph manager as an object to be informed ofany changes to said first data bearing object.
 16. The program storagedevice of claim 13 wherein said step of transmitting a messageindicating that said first data bearing object expects to undergo achange comprises the steps of:registering said object graph manager asan observer with said first data bearing object; broadcasting saidmessage indicating that said first data bearing object expects toundergo a change from said first data bearing object to registeredobservers of said data bearing object.
 17. The program storage device ofclaim 14 wherein said interested object comprises a user interfacemanager object managing values displayed in a user interface, andwherein said method steps further comprise the steps of:after said userinterface manager object has received said message indicating that saidfirst data bearing object has undergone a change, transmitting a messagefrom said user interface manager object to said first data bearingobject requesting values for data of said first data bearing object;transmitting said values for said data of said first data bearing objectfrom said first data bearing object to said user interface managerobject, updating said values displayed in said user interfacecorresponding to said values for said data of said first data bearingobject.
 18. A program storage device readable by a machine, tangiblyembodying a program of instructions executable by the machine to performmethod steps for modifying a database in accordance with changes made toan object graph comprising a plurality of data bearing objectscontaining data from said database, said method steps comprising thesteps of:prior to making any change to a first data bearing object insaid object graph, transmitting a message indicating an expected changeto said first data bearing object to an object graph manager; taking asnapshot of said first data bearing object upon said object graphmanager receiving said message indicating said expected change; makingone or more changes to said first data bearing object; transmitting acommit message to said object graph manager requesting that changes madeto said first data bearing object be committed to said database; takinga second snapshot of said first data bearing object upon said objectgraph manager receiving said commit message; detecting said one or morechanges to said first data bearing object by comparing said secondsnapshot to said first snapshot; storing data corresponding to saiddetected one or more changes in said database.
 19. The program storagedevice of claim 18 wherein said step of storing data corresponding tosaid detected one or more changes in said database comprises the step ofsending a change request from said object graph manager to an objectstore.
 20. The program storage device of claim 19 wherein said objectstore comprises an object store coordinator that interfaces between saidobject graph manager and a plurality of databases.
 21. The programstorage device of claim 20 wherein said plurality of databases comprisedatabases distributed over a computer network.
 22. A program storagedevice readable by a machine, tangibly embodying a program ofinstructions executable by the machine to perform method steps forundoing changes made to an object graph comprising a plurality of databearing objects containing data from a database, said method stepscomprising the steps of:prior to making any change to a first databearing object in said object graph in response to an event thatinitiates execution of application code, transmitting a messageindicating that said first data bearing object expects to undergo achange from said first data bearing object to an object graph manager;taking a snapshot of said first data bearing object upon said objectgraph manager receiving said message indicating said expected change;making one or more changes to said first data bearing object during saidexecution of application code in response to said event; transmitting amessage indicating an end of said execution of application code inresponse to said event to said object graph manager; recording saidsnapshot on an undo stack.
 23. The program storage device of claim 22wherein said method steps further comprise the step of determiningwhether a previous snapshot of said data bearing object has already beentaken during said execution of application code in response to saidevent prior to taking said snapshot of said data bearing, and takingsaid snapshot only if no such previous snapshot has been taken.
 24. Theprogram storage device of claim 22 wherein said method steps furthercomprise the steps of:recording said snapshot in a recent snapshot tableafter taking said snapshot; clearing said recent snapshot table afterrecording said snapshot on said undo stack.